1. Field
Example embodiments relate to a nonvolatile memory device including resistive nodes and methods of operating and fabricating the same.
2. Description of the Related Art
Nonvolatile memory devices (e.g., phase-change RAM (PRAM) devices or resistance RAM (RRAM) devices) operate by varying the resistance of resistive nodes. As semiconductor products demand higher data capacity, higher integration and more operation bits of the nonvolatile memory device may be required. As such, multi-bit nonvolatile memory devices are increasingly required.
Because faster data processing speed may be required to process extra data, it is necessary for nonvolatile memory devices to have higher operating speed and higher data capacity. For example, the operating speed of flash memory devices may be increased by using block erasing and/or flash erasing method.
Increased integration of nonvolatile memory devices has led to efforts in decreasing the operating current of the devices. However, nonvolatile memory devices using resistive nodes require a higher operating current. Decreasing the operating current may affect the variable resistance of the resistive nodes. Accordingly, conventional nonvolatile memory devices may have restrictions in decreasing the operating current.
For example, PRAM stores data using a resistance change resulting from changes of the crystalline state of a resistor. A higher current density, which limits the minimum operating current, may be needed to change the crystalline state of the PRAM device. Higher operating current causes short channel effects and inhibits advances in the integration of the PRAM. Therefore, attempts have been made to obtain a higher current density with a lower operating current by decreasing the size of the crystalline state change region of a phase change resistor.